1. Field
An embodiment of the present invention relates to illumination optical systems, exposure apparatus, optical element and manufacturing method thereof, and device manufacturing methods.
2. Description of the Related Art
In a typical exposure apparatus of this type, a light beam emitted from a light source is guided through a fly's eye lens as an optical integrator to form a secondary light source (generally, a predetermined light intensity distribution on an illumination pupil) as a substantial surface illuminant consisting of a large number of light sources. The light intensity distribution on the illumination pupil will be referred to hereinafter as an “illumination pupil luminance distribution.” The illumination pupil is defined as follows: by action of an optical system between the illumination pupil and a surface to be illuminated (which is a mask or wafer in the case of an exposure apparatus), the surface to be illuminated is kept as a Fourier transform plane of the illumination pupil.
Beams from the secondary light source are condensed by a condenser lens to superposedly illuminate a mask on which a predetermined pattern is formed. Light transmitted by the mask travels through a projection optical system to be focused on a wafer. In this manner, the mask pattern is projected (or transferred) to effect an exposure thereof on the wafer. The pattern formed on the mask is a highly integrated one and this microscopic pattern can be accurately transferred onto the wafer by obtaining a uniform illuminance distribution on the wafer.
There is a conventionally proposed illumination optical apparatus capable of continuously changing the illumination pupil luminance distribution (and, in turn, an illumination condition) (cf. Japanese Patent Application Laid-open No. 2002-353105).